The ingestion of live microorganisms called probiotics, some of which are bacteria, and in particular those which belong to the genus Lactobacillus, are particularly beneficial to one's health. As a matter of fact, they have been the subject matter of numerous studies demonstrating preventive clinical effects in various fields (e.g., in the fields of allergic manifestations, infectious diarrhoea and inflammatory diseases) and on certain physiological functions (e.g., the digestion of lactose, bowel transit and immunity). These probiotics are, in particular, capable of promoting proper functioning of intestinal flora, which are likely to affect the overall population. As a matter of fact, among other things, these bacteria produce other bacteriocins and lactic acid, which indirectly increase the digestibility of food products, promote intestinal peristalsis, and accelerate the evacuation of stools. Furthermore, these bacteria produce certain B-complex vitamins, and in general promote the absorption of vitamins and minerals, reduce blood cholesterol, strengthen the immune system and coat the mucous membranes of the intestines so as to protect against the invasion and activities of harmful microorganisms.
For this reason, the agroprocessing industries have been attempting for several years to incorporate such bacteria into their products.
Such products with added bacteria are traditionally dairy products, however, there is an advantage for the agroprocessing industry to develop other food products, particularly fruit-based ones.
Other fruit-based food products with added bacteria of the Lactobacillus type are already known in the prior art, e.g., in the international patent application WO 00/70972, and the European patent application EP 0113055.
However, it has been possible to observe bacterial growth in food products to which lactobacilli have been added, which, during storage of the products, results in the qualities thereof being altered by the production of gases and off-tastes, thereby making them unsuitable for consumption.
Numerous microorganisms are capable of decarboxylating substituted cinnamic acids such as trans-4-hydroxy-methoxy-cinnamic acid (ferulic acid) and trans-4-hydroxy-cinnamic acid (p-coumaric acid), in order to form the two following volatile compounds, respectively:
3-methoxy-4-hydroxystyrene (4-vinyl guaiacol) and 4-hydroxystyrene (4-vinyl phenol). These molecules are responsible for off-tastes of the “phenol, smoky, glove-like and medicinal” type. P-coumaric acid and decarboxylated ferulic acid activity was detected in bacteria of the Lactobacillus type. In particular, the lactobacilli known for these activities are as follows: L. brevis, L. crispatus, L. fermentum, L. plantarum, L. pentosus and L. paracasei (bibliog. Ref.: Van Beek, S and Priest FG-2000—“Decarboxylation of substituted cinnamic acids by lactic acid bacteria isolated during malt whisky fermentation—Applied and Environmental Microbiology, 66 (12): 5322-8). Strains of lactobacilli are thus capable of producing off-tastes from phenolic acids via biotransformation pathways.
At present, the solutions proposed in the prior art for solving this problem involving the production of gases and off-tastes consist of preserving the products at a temperature of between 4 and 8° C. and with a low fruit concentration (approximately 25%), for example, as in the international patent application WO 00/70972, filed by the PROBI company.
However, these solutions do not make it possible to propose products having a fruit concentration greater than 50%, and further comprising a significant concentration of live and stable bacteria of the Lactobillus genus. A significant concentration is understood to mean a population greater than or equal to 108 CFU/ml of product. Stable bacteria are understood to mean a bacterial population having reduced metabolic activity (production of gases and/or off-tastes, and acidification during limited and controlled storage conditions) when cold, i.e., at a temperature of between 4 and 10° C. The limited post-acidification is the result of a reduction in the concentration of organic acids present in the product, on the one hand, and, on the other hand, the low storage temperature of said product.
A fruit-based food product which is of the beverage or fruit puree type and which comprises stable, live probiotics, will have the advantage of providing the consumer with the benefits of fruits and probiotics.
The National Plan on Nutrition and Health advocates consumption of a minimum of five portions of fruits and vegetable per day. Observations conducted by numerous scientists show that consuming more fruits and vegetables makes it possible in particular, to reduce the cholesterol rate and lipid intake, and to limit the prevalence of obesity in children.
Several scientific studies suggest that probiotics can likewise play a leading role with regards to health. Each probiotic strain can offer specific health benefits. Among these benefits can be found: improved digestive system functioning and strengthened natural defenses. Some probiotics act by absorbing proteins and others produce vitamins. Some can likewise produce compounds that fight against the propagation of pathogenic bacteria and can therefore play a role in the intestinal ecosystem.
It would be desirable for the agroprocessing industry to be capable of preparing such food products, and that is the subject matter of this invention.
In order to increase the viability of bacteria, the European patent applications EP 0113055 and EP 0166238, filed by Kirin Beer, propose that the concentration of polyphenols in fruit juices, which are bacteriostatic components, be selectively reduced by placing the juices in contact with absorbing agents. In this case, the desired objective is to also promote fermentation of the bacteria and to not keep the initial population stable, as is the case according to this invention.
It is known in the prior art that fruits contain organic acids, and the inventors have observed that bacteria of the Lactobacillus genus metabolize these organic acids, and that this metabolization of organic acids can be responsible for the production of carbon dioxide and/or off-tastes in fruit-based products. The organic acid compositions of some fruits can also be known by consulting bibliographic sources, e.g., such as the acidity ranges per fruit in the “Code of Practice” of the A.I.J.N.
Numerous strains of the Leuconostoc, Streptococcus and Lactobacillus genera are capable of degrading malate, citrate, pyruvate, fumarate, tartrate and gluconate in order to produce gases. In comparison to the measurement of gas produced, the determination of diacetyl and acetoin contents is a more effective method for detecting pyruvate degradation (Hegazi, F. Z., Abo-Elnaga, I. G., 1980. “Degradation of organic acids by dairy lactic acid bacteria. Mikrobioligie der Landwirtshaft der Technologie and des Umweltschutzes, 135 (3), 212).
When degraded, organic acids such as malic acid or citric acid do not, as a matter of fact, present the consumer with these problematics involving the generation of unpleasant tastes, unless this assimilation is accompanied by an excessively high production of acetate, which also produces off-tastes. However, the assimilation of these organic acids by bacterial strains will in this case produce CO2, which will inflate the product packaging. As a matter of fact, these organic acids are metabolized naturally by certain species of lactobacilli, in order to produce pyruvate (the principal compound of metabolic cycles such as carbonaceous metabolism) and CO2; furthermore, pyruvate is itself subject to decarboxylation reactions, thus proportionally increasing the rates of CO2 produced.
Some of these organic acids are phenolic compounds (coumaric acid, ferulic acid) and the degradation of these compounds by bacterial strains may produce off-tastes in the product.
Depending on the pH of the end product, the sensory profile of an acid is highly variable. Thus, lactic acid is more astringent at pH 3.5 in comparison to citric acid and malic acid (Hartwig, P., McDaniel, M. R., 1995. “Flavor characteristics of lactic, malic, citric and acetic acids at various pH levels.” Journal of Food Science, 60 (2), 384-388.).
FIG. 1 thus shows the mechanism of metabolism for malic acid (or malate), citric acid (or citrate) and pyruvate.
Commercial beverages exist, in particular the product ProViva® distributed by Skånemejerier, which contain a strain of the Lactobacillus genus at a maximum concentration equal to 108 CFU/ml and at an acid pH (pH=3.8). However, the stability of the product is only guaranteed when stored at 4° C. and as the result of a low concentration of fruit juices (<25%). Furthermore, the ProViva® commercial products have targeted certain types of fruits which have low organic acid concentrations and which do not include major juices like orange juice, apple juice and exotic multi-fruit juices.